How to Fry your power transformer

I copied this from a posting on the hallicrafters mailing list that I recently joined, thanks to Lorne in Nanaimo. Thought this was quite interesting the the

Message 1 of 2
, Oct 2, 2012

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I copied this from a posting on the hallicrafters mailing list that I recently joined, thanks to Lorne in Nanaimo. Thought this was quite interesting the the message calls a 5V4 a "death tube" anyone else heard or seen anthing along this topic line. Anyone know of other dangerous rectifiers prone to short out and ruin a radio transformer?

Lesson learned the hard way. If you have one of these fine transmitters
and if it is still using the 5V4 low voltage rectifier, your power
transformer is in danger. If I remember correctly the problem is caused
by a cathode to plate short in the 5V4 which opens the high voltage
winding in the PT. These transformers are very hard to find and
expensive if you can find one. I purchased a beautiful HT-32A several
years back knowing that the PT was bad. I was able to order a
replacement PT from the Peter Dahl Co. Expensive but a perfect
replacement and runs very cool. I replaced that 5V4 with a 5R4 in this
and my HT-37. I am told that those 5V4s have killed many a transformer
and some call it a "death tube." You might while you are in there
replace the selenium bias rectifier with a silicon rectifier. There
have been many articles dealing with these modifications on the HT-32s
and HT-37s.

lbohn@shaw.ca

I have tried to be vigilant about replacing the selenium bias rectifier with a silicon rectifier as well. It probably isn’t a big concern with tube sets but

Message 2 of 2
, Oct 2, 2012

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I have tried to be vigilant about replacing the selenium bias rectifier
with a silicon rectifier as well. It probably isn’t a big concern with
tube sets but I have a pinball machine that needs a “heads up”. I’m sure
the audio guys on the list have a lot more information about them than I
have.

I copied this from a posting on the hallicrafters mailing list that I
recently joined, thanks to Lorne in Nanaimo. Thought this was quite interesting
the the message calls a 5V4 a "death tube" anyone else heard or seen anthing
along this topic line. Anyone know of other dangerous rectifiers prone to short
out and ruin a radio transformer?

Lesson learned the hard way. If you have one of these fine
transmittersand if it is still using the 5V4 low voltage rectifier, your
powertransformer is in danger. If I remember correctly the problem is
causedby a cathode to plate short in the 5V4 which opens the high
voltagewinding in the PT. These transformers are very hard to find
andexpensive if you can find one. I purchased a beautiful HT-32A
severalyears back knowing that the PT was bad. I was able to order
areplacement PT from the Peter Dahl Co. Expensive but a
perfectreplacement and runs very cool. I replaced that 5V4 with a 5R4 in
thisand my HT-37. I am told that those 5V4s have killed many a
transformerand some call it a "death tube." You might while you are in
therereplace the selenium bias rectifier with a silicon rectifier.
Therehave been many articles dealing with these modifications on the
HT-32sand HT-37s.

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